CVE-2010-5076 in Digia
Summary
by MITRE
QSslSocket in Qt before 4.7.0-rc1 recognizes a wildcard IP address in the subject s Common Name field of an X.509 certificate, which might allow man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
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Analysis
by VulDB Data Team • 12/05/2021
The vulnerability described in CVE-2010-5076 represents a critical security flaw in the Qt framework's QSslSocket implementation that affects versions prior to 4.7.0-rc1. This issue stems from improper handling of X.509 certificate validation logic, specifically concerning wildcard IP addresses within the subject's Common Name field. The flaw creates a significant bypass of SSL/TLS security mechanisms that are designed to prevent man-in-the-middle attacks by ensuring server authenticity through proper certificate validation. When a certificate contains a wildcard IP address in its Common Name field, the vulnerable Qt implementation incorrectly accepts it as valid for any IP address, effectively undermining the cryptographic security assurances that SSL/TLS protocols are meant to provide.
The technical root cause of this vulnerability lies in the certificate validation process where QSslSocket fails to properly enforce the standard X.509 certificate validation rules. According to industry standards such as RFC 5280 and CWE-295, proper certificate validation requires strict matching between the certificate's subject identifiers and the actual server being connected to. The flaw allows an attacker to craft a certificate with a wildcard IP address in the Common Name field, which the vulnerable Qt implementation accepts without proper verification. This behavior violates the fundamental principle of certificate validation where IP addresses should be matched against the certificate's subject alternative names or common name fields according to established security protocols. The vulnerability specifically targets the certificate verification logic that should enforce strict matching between the presented certificate and the expected server identity.
The operational impact of this vulnerability is severe and directly enables sophisticated man-in-the-middle attack scenarios. An attacker who has obtained a legitimate certificate from a trusted Certification Authority can create a malicious certificate containing a wildcard IP address in the Common Name field, allowing them to impersonate any server within that IP range. This creates a dangerous situation where network traffic intended for legitimate servers can be intercepted and modified without detection, as the SSL/TLS connection would appear valid to applications using the vulnerable Qt framework. The attack vector is particularly concerning because it leverages the trust relationship between the client application and the Certification Authority, making it difficult for end users to detect the compromise. This vulnerability affects any application built with Qt versions prior to 4.7.0-rc1 that rely on QSslSocket for secure communications, potentially exposing sensitive data, credentials, and system resources to unauthorized access.
Mitigation strategies for this vulnerability require immediate upgrading of affected Qt framework versions to 4.7.0-rc1 or later, where the certificate validation logic has been corrected to properly enforce X.509 certificate standards. Organizations should conduct comprehensive inventory assessments to identify all applications using vulnerable Qt versions and prioritize their remediation. Additionally, security teams should implement network monitoring to detect potential exploitation attempts and consider temporary network segmentation or firewall rules to limit exposure. The fix implemented in Qt 4.7.0-rc1 addresses the core validation logic by ensuring that wildcard IP addresses in the Common Name field are properly validated against the actual connection target, aligning with established security practices and ATT&CK framework techniques related to credential access and defense evasion. This vulnerability highlights the importance of proper certificate validation implementation and demonstrates how seemingly minor implementation flaws can create significant security risks in cryptographic systems.